Generally, a portable hard disk must be assembled with a shock and vibration proof assembly so as to protect the data stored in the hard disk without being destroyed due to collision and falling out. Thus the work will not stop because the data in the hard disk can be read.
Referring to FIG. 1, a prior art hard disk with vibration proof structure disclosed in Taiwan Patent No. M272203 or 539219 is illustrated. In that, a lower casing 11 of a portable memory device 10 is installed with a plurality of supporting posts 111. Each post 111 is enclosed by a soft adhesive glue 112. A hard disk 10 is fixed to a circuit board 12. The circuit board 12 with the hard disk 10 is retained to the soft adhesive glue 112 with the hard disk 10 being suspended so as to have a preferred vibration proof effect. In the patent M272203, inner sides of an upper casing and a lower casing are installed with vibration roof material which is positioned as the upper casing and lower cover are combined. From above prior arts, it is known that the vibration proof structure is very important.